Electrodeposited nano-flower like NiCo-LDH as a superior pseudo-capacitive electrode material for supercapacitors

Layered double hydroxides (LDH) are promising electrode materials for supercapacitors, because of their high specific capacitance, better electronic conductivity and good cycling stability. At present, nickel cobalt based LDH are investigated due to high synergistic effects like high electrical conductivity and cycling stability for the development of pseudo-capacitive materials. Among various synthesis methods, facile electrodeposition method is an effective technique to prepare binder free high purity and conductive materials in less time duration. Highlighting this, we demonstrate here a simple one-step galvanostatic electrodeposition method to prepare NiCo-LDH on nickel foam and compared its pseudo-capacitive performance with either Ni hydroxides or Co hydroxides. The surface morphology characterization by scanning electron microscopy confirms that the layered double hydroxides are formed with nanoflower like morphology. The electrochemical active surface area and the diffusion coefficients of the NiCo-LDH electrode are found to be 4.88 cm²and 7.3 × 10⁻⁴ cm² s⁻¹(anodic) and 3.6 × 10⁻⁴ cm² s⁻¹(cathodic), respectively. Interestingly, the NiCo-LDH provide a high specific capacitance of 808 F g⁻¹(363C g⁻¹) compared to 304 F g⁻¹(136C g⁻1) for α-Co(OH)₂, when cycled at 1 A g⁻¹in 1 M KOH solution. It also demonstrates better cycling stability, retaining about 61 % of its capacitance after 3000 cycles. In contrast, α-Ni(OH)₂ and α-Co(OH)₂ retain only about 54 % and 74 % of their capacitance, respectively after 3000 cycles, when cycled at 5 A g⁻¹. Additionally, NiCo-LDH can provide 429 F g⁻¹compared to 304 F g⁻¹for Ni(OH)₂ when cycled at 10 A g⁻¹, showing its better rate performance. Therefore, the electrodeposited NiCo-LDH can be a promising electrode material for supercapacitors.